dd0201 dd0203 optorite reading burning problem DVD+R

[frank_mazda]

Hi,
I have an OPTORITE dd0201 (2.50E).
I never had problems except this one.
I'm backing up (different softwares, the result doesn not change) some movies on DVD+R (different brands, the result is the same).
I don't get any error.
When playing (with any player/stand alone /drive) some of them are not readable beyond 40-50% of the movie (while before it's all perfect). It's as if the disc was massively scratched after a certain point (but the disc is PERFECT).
This for now never happened w/ DVD-R (but I burned only 4 DVD-R).
Is it my drive ?
Is it the media (imation or kypermedia) ?
thank you in advance

[frank_mazda]

OK it happened even with a DVD-R. I may be have an explanation and would be happy if anybody got the same problem. I got these coasters if I was trying pretty heavy multitasking (100%CPU while I was burning or decoding I was decoding/compressing another DVD on the other drive). Could that be the reason (but I didn't get any warning or buffer underruns) ?